Geomagnetic storms can result in large magnetic field disturbances and intense currents in the magnetosphere and even on the ground.As an important medium of momentum and energy transport among the solar wind,magnetos...Geomagnetic storms can result in large magnetic field disturbances and intense currents in the magnetosphere and even on the ground.As an important medium of momentum and energy transport among the solar wind,magnetosphere,and ionosphere,field-aligned currents(FACs)can also be strengthened in storm times.This study shows the responses of FACs in the plasma sheet boundary layer(PSBL)observed by the Magnetospheric Multiscale(MMS)spacecraft in different phases of a large storm that lasted from May 27,2017,to May 29,2017.Most of the FACs were carried by electrons,and several FACs in the storm time also contained sufficient ion FACs.The FAC magnitudes were larger in the storm than in the quiet period,and those in the main phase were the strongest.In this case,the direction of the FACs in the main phase showed no preference for tailward or earthward,whereas the direction of the FACs in the recovery phase was mostly tailward.The results suggest that the FACs in the PSBL are closely related to the storm and could be driven by activities in the tail region,where the energy transported from the solar wind to the magnetosphere is stored and released as the storm is evolving.Thus,the FACs are an important medium of energy transport between the tail and the ionosphere,and the PSBL is a significant magnetosphere–ionosphere coupling region in the nightside.展开更多
In this investigation effort, we eventually infer that the overall quadrapole pattern of B<sub>y</sub> deflections, in the vicinity of a source in the Earth’s magnetotail, is most likely due to field alig...In this investigation effort, we eventually infer that the overall quadrapole pattern of B<sub>y</sub> deflections, in the vicinity of a source in the Earth’s magnetotail, is most likely due to field aligned currents (FACs) and not to Hall currents associated with an X-type collisionless reconnection. This categorically expressed statement is based upon sufficient observational evidence tightly associated with our own suggested model and the preceded works of the same author. Using representative events measured by satellite, our main aim is to describe the nature of the fundamental mechanism determining the polarity of the B<sub>y</sub> deflections associated with intense earthward ionplasma flows. A major finding is that we either observe magnetic flux rope (MFR) like structures (that is, entities having all the morphological features of ropes; i.e., a dipolar signature of B<sub>z</sub> occurring simultaneously with peaked B<sub>y</sub> and B<sub>total</sub> deflections) or mere B<sub>y</sub> deflections, however, the sign for all these (B<sub>y</sub>deflections) is always determined by the satellite placement in north (positive) or south (negative) plasma sheet. Therefore, the MFR-like structures located earthward of the source are most likely pseudo-MFRs;there is neither a tubular topology nor an axial magnetic field, the B<sub>y</sub> deflections are produced by FACs. According to the presented model, a fundamental concept is that both ions and electrons are simultaneously accelerated at the source site;in turn, the earthward streaming electrons (ions) form a bifurcated electron (ion) FAC just outside the electron diffusion region-EDR (IDR). In this way, inside the IDR (and earthward of the source) positive (negative) B<sub>y</sub> deflections in north (south) plasma sheet (PS) are produced due to FACs, and not to (inward) Hall currents as in the context of an X-line. Moreover, the ions form an “ion jet” within the IDR, while just outside this region they produce positive (negative) B<sub>y</sub> deflections in north (south) PS caused by ion FACs. The ion jet in the IDR is enveloped by the bifurcated electron FAC. Eventually, although the resulting pattern of B<sub>y</sub> deflections, due to both electron and ion FACs, is apparently the same with that resulting from Hall currents (in the X-line model), the underlying natural processes are, however, radically different. Certainly, the dominant “spatial entity” within the IDR is the ion jet-current (and not the Hall-electron current). Additional implications of the ion jets are also discussed.展开更多
A combined action of plasma convection and pitch-angle diffusion of electrons and protons leads to the formation of plasma pressure distribution in the magnetosphere on the night side, and, as it is known, steady elec...A combined action of plasma convection and pitch-angle diffusion of electrons and protons leads to the formation of plasma pressure distribution in the magnetosphere on the night side, and, as it is known, steady electric bulk currents are connected to distribution of gas pressure. The divergence of these bulk currents brings about a spatial distribution of field-aligned currents, i.e. magnetospheric sources of ionospheric current. The projection (mapping) of the plasma pressure relief onto the ionosphere corresponds to the form and position of the auroral oval. This projection, like the real oval, executes a motion with a change of the convection electric field, and expands with an enhancement of the field. Knowing the distribution (3D) of the plasma pressure we can determine the places of MHD-compressor and MHD-generators location in the magnetosphere. Unfortunately, direct observations of plasma distribution in the magnetosphere are faced with large difficulties, because pressure must be known everywhere in the plasma sheet at high resolution, which in situ satellites have been unable to provide. Modeling of distribution of plasma pressure (on ~ 3-12 Re) is very important, because the data from multisatellite magnetospheric missions for these purposes would be a very expensive project.展开更多
A 3-dimensional resistive MHD simulation was carried out to study the effect of the upward ions on the field-aligned currents (FACs) in the near-earth magnetotail. The simulation results show that the up-flow ions ori...A 3-dimensional resistive MHD simulation was carried out to study the effect of the upward ions on the field-aligned currents (FACs) in the near-earth magnetotail. The simulation results show that the up-flow ions originating from the nightside auroral oval would drift into the center plasma sheet along the magnetic field lines in the plasma sheet boundary, and have an important effect on the field-aligned currents. The main conclusions include that: 1) the upward-ions mainly affect the field- aligned currents in the near-earth magnetotail (inside 15 Re); 2) the generated FACs in the near-earth region have two types, i.e., Region 1 FAC in the high-latitude and Region 2 FAC in the low-latitude; 3) FACs increase with the enhancement of the upward ion flux; 4) with the same flux of the upward ions, FACs enhance with the increase of the velocity of the up-flow ions; 5) the intensification of FACs is also closely related with the latitude of the upward ions, and the ions from the closed field line region generate larger FACs; 6) the generation of FACs is closely related with By created by the upward ions.展开更多
A three-dimensional (3-D) Hall MHD simulation is carried out to study the roles of initial current carrier in the topology of magnetic field, the generation and distribu- tion of field aligned currents (FACs), and the...A three-dimensional (3-D) Hall MHD simulation is carried out to study the roles of initial current carrier in the topology of magnetic field, the generation and distribu- tion of field aligned currents (FACs), and the appearance of Alfvén waves. Consid- ering the contribution of ions to the initial current, the topology of the obtained magnetic field turns to be more complex. In some cases, it is found that not only the traditional By quadrupole structure but also a reversal By quadrupole structure appears in the simulation box. This can explain the observational features near the diffusion region, which are inconsistent with the Hall MHD theory with the total ini- tial current carried by electrons. Several other interesting features are also emerged. First, motions of electrons and ions are decoupled from each other in the small plasma region (Hall effect region) with a scale less than or comparable with the ion inertial length or ion skin depth di=c/ωp. In the non-Hall effect region, the global magnetic structure is shifted in +y direction under the influence of ions with initial y directional motion. However, in the Hall effect region, magnetic field lines are bent in ?y direction, mainly controlled by the motion of electrons, then By is generated. Second, FACs emerge as a result of the appearance of By. Compared with the prior Hall MHD simulation results, the generated FACs shift in +y direction, and hence the dawn-dusk symmetry is broken. Third, the Walén relation in our simulations is consistent with the Walén relation in Hall plasma, thus the presence of Alfvén wave is confirmed.展开更多
Field-aligned currents in the inner magnetosphere arc studied by using ISEE-2 magnetometer da-la, A method is proposed to calculate ×B with single-satellite data. From the morphology of ×B in time (or L). a ...Field-aligned currents in the inner magnetosphere arc studied by using ISEE-2 magnetometer da-la, A method is proposed to calculate ×B with single-satellite data. From the morphology of ×B in time (or L). a lot of large fluctuations are found in ×B near L = 5.5RE corresponding to the field-aligned currents. Statistical study shows that the field-aligned current in the inner magnetosphere is a function of B, L, MLT and AL. The region of the projections of ×B along the magnetic field line onto the ionosphere is not symmetrical for the geomagnetic pole. The inner boundary is independent of the geomagnetic disturbance, but during substorms the outer boundary shifts equatorward. The spatial distribution of the in- and out-flowing currents is complicated. The region-1-and-2 system is hardly distinguishable.展开更多
Using the east-west geomagnetic disturbance fields observed from stations at mid-latitudes,we investigate the characteristics of field-aligned currents on the nightside during the April 6,2000 superstorm.The results i...Using the east-west geomagnetic disturbance fields observed from stations at mid-latitudes,we investigate the characteristics of field-aligned currents on the nightside during the April 6,2000 superstorm.The results indicate that there is an eastward disturbance on the nightside of Northern Hemisphere during the main phase of magnetic storm,while the interplanetary magnetic field(IMF)is continued southward.The positive disturbances in the postmidnight are larger than that in the premidnight.This suggests that upward field-aligned currents develop on the nightside,when the IMF is directed southward.The peak of upward fieldaligned currents is located in postmidnight,and it will be more obvious at substorm expansion.We get the conclusion that both partial ring current and region-2 field-aligned current shift to dusk sector.The upward region-2 current is decreased at substorm onset,and intensified after it.We also investigate the relationship between the upward field-aligned currents on the nightside and the auroral electrojets at high latitudes.It shows a good correspondence between region-2 current and the westward electrojet in the postmidnight.We suppose that they are both associated with the convection electric field.展开更多
Low-density short-duration pulsed current-assisted aging treatment was applied to the Ti-6Al-4V-0.5Mo-0.5Zr alloy subjected to different solution treatments.The results show that numerous α_(p) phases redissolve into...Low-density short-duration pulsed current-assisted aging treatment was applied to the Ti-6Al-4V-0.5Mo-0.5Zr alloy subjected to different solution treatments.The results show that numerous α_(p) phases redissolve into the new β phase during the pulsed current-assisted aging process,and then the newly formed β phase is mainly transformed into the β_(t) phase,with occasional transition to new α_(p) phase,leading to a remarkable grain refinement,especially for the lamellarαs phases.In comparison to conventional aging treatment,the pulsed current-assisted aging approach achieves a significant enhancement in strength without degrading ductility,yielding an excellent mechanical property combination:a yield strength of 932 MPa,a tensile strength of 1042 MPa,and an elongation of 12.2%.It is primarily ascribed to the increased fraction of β_(t) phases,the obvious grain refinement effect,and the slip block effect induced by the multiple-variantαs colonies distributed within β_(t) phases.展开更多
Two-dimensional(2D)MoS_(2) is considered an excellent candidate material for nextgeneration photodetectors.However,the high dark current and low photocurrent in MoS_(2) devices severely hinder their practical applicat...Two-dimensional(2D)MoS_(2) is considered an excellent candidate material for nextgeneration photodetectors.However,the high dark current and low photocurrent in MoS_(2) devices severely hinder their practical application.Strategies for suppressing dark current and enhancing photocurrent should be explored.Herein,we propose a modification strategy for MoS_(2) by utilizing Ag_(70) nanoclusters(NCs)as electron reservoirs and photoabsorbers to suppress dark current and enhance the photocurrent of 2D MoS_(2) photodetector.Remarkably,the dark current is effectively suppressed by four orders of magnitude,while the photocurrent is enhanced by over tenfold upon modification with Ag_(70) NCs,compared to the pristine MoS_(2) photodetector.The reduction in dark current is attributed to charge transfer from MoS_(2) to Ag_(70) NCs owing to the strong electronwithdrawing property of Ag_(70) NCs.The increase in photocurrent benefits from enhanced optical absorption of the photodetector after Ag_(70) NCs modification and the subsequent injection of photoexcited electrons from Ag_(70) NCs to MoS_(2).Compared to isolated MoS_(2),the modulated photodetector shows exceptional improvements in several key figures of merit(such as responsivity,detectivity,external quantum efficiency,and photoswitching on/off ratio).This study opens up new avenues for building high-performance 2D MoS_(2) photodetectors.展开更多
With geomagnetic measurements on board of CHAMP satellite, the characteristics of global large-scale field-aligned currents (FACs) in the topside ionosphere are investigated along with their responses to interplanetar...With geomagnetic measurements on board of CHAMP satellite, the characteristics of global large-scale field-aligned currents (FACs) in the topside ionosphere are investigated along with their responses to interplanetary conditions for the superstorm of November, 2003. It is found that (1) The storm-time FAC densities enhanced greatly in comparison with quiet period and the enhancements show hemispheric asymmetry of both summer-winter and sunlit-dark. (2) For the first time, it is revealed that the lati-tude-integrated FAC density is controlled mainly by solar wind dynamic pressure rather than IMF. (3) FACs expanded equatorward dramatically, with the lowest latitude being 45° MLat or more; on the day-side this expansion was controlled directly by IMF Bz, showing an interaction time scale of about 25 min in the solar wind-magnetosphere-ionosphere coupling system, and a nonlinear saturation of the equatorward expansion when IMF Bz < -30 nT; while on the nightside, the expansion and recovery lagged about 3 h behind the IMF changes but nearly in phase with changes of SYM-H index. (4) During the storm main phase, the nightside FAC latitude coverage extended to 25° or wider, appearing multi-sheet current structure with more than 10 sheets.展开更多
Accurate modeling of Earth's ionospheric F-region currents is essential for refining geomagnetic field models and understanding magnetosphere-ionosphere coupling.In this study,we develop averaged models to charact...Accurate modeling of Earth's ionospheric F-region currents is essential for refining geomagnetic field models and understanding magnetosphere-ionosphere coupling.In this study,we develop averaged models to characterize F-region currents using magnetic data from the MSS-1(Macao Science Satellite-1) and Swarm satellite missions.Our approach employs a toroidal field representation,utilizing spherical harmonics to capture spatial variations and Fourier series to represent temporal dynamics.Two models,Model-A and Model-B,derived from distinct datasets,are constructed to represent current patterns at altitudes of 450 km and 512 km,respectively.Our models successfully capture the primary spatial structures and seasonal variations of polar field-aligned currents.Additionally,they accurately reproduce the localized inter-hemispheric field-aligned currents observed in mid and low latitudes during solstices,particularly between 14:00 and 16:00 magnetic local times.These findings enhance our understanding of ionospheric F-region currents and contribute to more precise geomagnetic field modeling.展开更多
Field-aligned coordinates have been implemented in the gyrokinetic semi-Lagrangian code NLT, Ye et al （2016 J. Comput. Phys. 316 180）, to improve the computational efficiency for the numerical simulations of tokamak...Field-aligned coordinates have been implemented in the gyrokinetic semi-Lagrangian code NLT, Ye et al （2016 J. Comput. Phys. 316 180）, to improve the computational efficiency for the numerical simulations of tokamak turbulence and transport. 4D B-spline interpolation in field- aligned coordinates is applied to solve the gyrokinetic Vlasov equation. A fast iterative algorithm is proposed for efficiently solving the quasi-neutrality equation. A pseudo transform method is used for the numerical integration of the gyro-average operator for perturbations with a high toroidal mode number. The new method is shown to result in an improved code performance for reaching a given accuracy. Some numerical tests are presented to illustrate the new methods.展开更多
The multi-terminal direct current(DC)grid has extinctive superiorities over the traditional alternating current system in integrating large-scale renewable energy.Both the DC circuit breaker(DCCB)and the current flow ...The multi-terminal direct current(DC)grid has extinctive superiorities over the traditional alternating current system in integrating large-scale renewable energy.Both the DC circuit breaker(DCCB)and the current flow controller(CFC)are demanded to ensure the multiterminal DC grid to operates reliably and flexibly.However,since the CFC and the DCCB are all based on fully controlled semiconductor switches(e.g.,insulated gate bipolar transistor,integrated gate commutated thyristor,etc.),their separation configuration in the multiterminal DC grid will lead to unaffordable implementation costs and conduction power losses.To solve these problems,integrated equipment with both current flow control and fault isolation abilities is proposed,which shares the expensive and duplicated components of CFCs and DCCBs among adjacent lines.In addition,the complicated coordination control of CFCs and DCCBs can be avoided by adopting the integrated equipment in themultiterminal DC grid.In order to examine the current flow control and fault isolation abilities of the integrated equipment,the simulation model of a specific meshed four-terminal DC grid is constructed in the PSCAD/EMTDC software.Finally,the comparison between the integrated equipment and the separate solution is presented a specific result or conclusion needs to be added to the abstract.展开更多
Advanced OER/HER electrocatalytic alternatives are crucial for the wide adaptation of green hydrogen energy.Herein,Ru/NiMnB spherical cluster pillar(SCP),denoted as Ru/NiMnB,is synthesized using a combination of elect...Advanced OER/HER electrocatalytic alternatives are crucial for the wide adaptation of green hydrogen energy.Herein,Ru/NiMnB spherical cluster pillar(SCP),denoted as Ru/NiMnB,is synthesized using a combination of electro-deposition and hydrothermal reaction.Systematic investigation of Ru doping in the NiMnB matrix revealed significant improvements in electrocatalytic performance.The Ru/NiMnB SCPs demonstrate superior OER/HER activity with low overpotentials of 150 and 103 mV at 50mA/cm^(2)in 1 M KOH,making them highly competitive with state-of-the-art electrocatalysts.Remarkably,the Ru/NiMnB SCPs exhibit a low 2-E cell voltage of 2.80 V at ultra-high current density of 2,000 m A/cm^(2)in 1 M KOH,outperforming the standard benchmark electrodes of RuO_(2)||Pt/C,thereby positioning Ru/NiMnB as one of the best bifunctional electrocatalysts.These SCPs exhibit exceptional high-current characteristics,stability and corrosion resistance,as evidenced by continuous operation at 1,000 mA/cm^(2)high-current density for over 150 h in 6 M KOH at elevated temperatures under harsh industrial conditions.Only a small amount of Ru incorporation significantly enhances the electrocatalytic performances of NiMnB,attributed to increased active sites and improved intrinsic properties such as conductivity,adsorption/desorption capability and reaction rates.Consequently,Ru/NiMnB SCPs present a promising bi-functional electrode concept for efficient green H_(2)production.展开更多
This work demonstrates experimentally the close relation between return currents from relativistic laser-driven target polarization and the quality of the relativistic laser–plasma interaction for laser-driven second...This work demonstrates experimentally the close relation between return currents from relativistic laser-driven target polarization and the quality of the relativistic laser–plasma interaction for laser-driven secondary sources,taking as an example ion acceleration by target normal sheath acceleration.The Pearson linear correlation of maximum return current amplitude and proton spectrum cutoff energy is found to be in the range from~0.70 to 0.94.kA-scale return currents rise in all interaction schemes where targets of any kind are charged by escaping laser-accelerated relativistic electrons.Their precise measurement is demonstrated using an inductive scheme that allows operation at high repetition rates.Thus,return currents can be used as a metrological online tool for the optimization of many laser-driven secondary sources and for diagnosing their stability.In particular,in two parametric studies of laser-driven ion acceleration,we carry out a noninvasive online measurement of return currents in a tape target system irradiated by the 1 PW VEGA-3 laser at Centro de Láseres Pulsados:first the size of the irradiated area is varied at best compression of the laser pulse;second,the pulse duration is varied by means of induced group delay dispersion at best focus.This work paves the way to the development of feedback systems that operate at the high repetition rates of PW-class lasers.展开更多
BACKGROUND Diabetic gastroparesis(DGP)disrupts gastric motility.Electroacupuncture(EA)at Zusanli(ST36)may alleviate DGP symptoms via neural pathways.AIM To investigate how EA current intensities at ST36 regulate neura...BACKGROUND Diabetic gastroparesis(DGP)disrupts gastric motility.Electroacupuncture(EA)at Zusanli(ST36)may alleviate DGP symptoms via neural pathways.AIM To investigate how EA current intensities at ST36 regulate neural pathways and improve gastric motility in DGP models.METHODS A DGP model was established using intraperitoneal injection of streptozotocin.Gastrointestinal motility was measured in rats after 2 weeks of continuous EA at ST36.Current intensity was selected as 0.5 mA,1 mA,and 3 mA.Gastric electrodynamics were detected by recording and analyzing the number of gastric discharges.The gastric emptying rate and propulsion rate of the small intestine were measured to assess dynamic gastrointestinal function.Hematoxylin-eosin staining was conducted to measure histopathological changes in the gastric sinus.Reverse transcription-polymerase chain reaction was conducted to determine mRNA levels of Rho guanine nucleotide-binding protein A and Rho-associated coiled-coil forming protein kinase.Western blotting was conducted to determine the expression levels of choline acetyltransferase,tyrosine hydroxylase,Rho guanine nucleotide-binding protein A,and Rho-associated coiled-coil forming protein kinase.Immunofluorescence staining in the stomach was conducted to detect the distribution of C-kit,an interstitial cell of Cajal marker.An enzymelinked immunosorbent assay was conducted to detect serum levels of acetylcholine and norepinephrine.RESULTS Treatment with EA improved gastric emptying and gastric smooth muscle disorders in rats with DGP,mitigated pathological damage,and restored the function of interstitial cells of Cajal.In addition,different current intensities of EA affected gastrointestinal function of rats with DGP.The 0.5 mA,1 mA,and 3 mA EA groups all improved gastrointestinal function.0.5 mA EA increased acetylcholine levels by increasing protein expression of choline acetyltransferase(P<0.05),thereby upregulating vagus nerve activity and enhancing parasympathetic nerve regulation.3 mA EA increased norepinephrine levels(P<0.05)by increasing protein expression of tyrosine hydroxylase,thereby activating the sympathetic nervous pathway.1 mA coordinated the function of the vagus and sympathetic nerves to improve gastrointestinal motility.CONCLUSION EA with ST36 improved gastric motility in rats with DGP.0.5 mA EA activated the vagus nerve,while 3 mA EA regulated gastrointestinal motility by activating the sympathetic nerves.展开更多
Non-metallic inclusions in steel are a significant challenge,affecting material properties and leading to issues such as stress concentration,cracking,and accelerated corrosion.Current methods for removing inclusions,...Non-metallic inclusions in steel are a significant challenge,affecting material properties and leading to issues such as stress concentration,cracking,and accelerated corrosion.Current methods for removing inclusions,including bubble,electromagnetic stirring,filtration separation,fluid flow,and sedimentation,often struggle with the removal of fine inclusions.Apart from these known methods,pulsed electric current(PEC),as an emerging technology,has demonstrated immense potential and environmental advantages.PEC offers adjustable current parameters and simple equipment,making it an attractive alternative to traditional methods.Its green energy-saving features and excellent results in regulating inclusion morphology and migration,as well as inhibiting submerged entry nozzle(SEN)clogging,make it a promising technology.In comparison to continuous current technology,PEC has shown significant advantages in regulating inclusions,not only improving purification efficiency but also demonstrating outstanding performance in flow stability and energy consumption.The ability of PEC to efficiently reduce inclusion numbers enhances the purity and quality of molten steel,improving its mechanical properties.Currently,the theoretical basis for controlling the movement of inclusions by current is mainly composed of three major theories:the double electric layer theory,electromagnetic force reverse separation theory,and electric free energy drive theory.These theories together form an important framework for researchers to understand and optimize the behavior of impurity movement controlled by electric current.Looking ahead,PEC is expected to pave the way for new solutions in directional regulation of inclusion migration,efficient inclusion removal,SEN clogging prevention,and the purification of molten steel.展开更多
Micron-sized silicon(μSi)is a promising anode material for next-generation lithium-ion batteries due to its high specific capacity,low cost,and abundant reserves.However,the volume expansion that occurs during cyclin...Micron-sized silicon(μSi)is a promising anode material for next-generation lithium-ion batteries due to its high specific capacity,low cost,and abundant reserves.However,the volume expansion that occurs during cycling leads to the accumulation of undesirable stresses,resulting in pulverization of silicon microparticles and shortened lifespan of the batteries.Herein,a composite film of Cu-PET-Cu is proposed as the current collector(CC)forμSi anodes to replace the conventional Cu CC.Cu-PET-Cu CC is prepared by depositing Cu on both sides of a polyethylene terephthalate(PET)film.The PET layer promises good ductility of the film,permitting the Cu-PET-Cu CC to accommodate the volumetric changes of silicon microparticles and facilitates the stress release through ductile deformation.As a result,theμSi electrode with Cu-PET-Cu CC retains a high specific capacity of 2181 mA h g^(-1),whereas theμSi electrode with Cu CC(μSi/Cu)exhibits a specific capacity of 1285 mA h g^(-1)after 80 cycles.The stress relieving effect of CuPET-Cu was demonstrated by in-situ fiber optic stress monitoring and multi-physics simulations.This work proposes an effective stress relief strategy at the electrode level for the practical implementation ofμSi anodes.展开更多
The stability and electrocatalytic efficiency of transition metal oxides for water splitting is determined by geometric and electronic structure,especially under high current densities.Herein,a newly designed lamella-...The stability and electrocatalytic efficiency of transition metal oxides for water splitting is determined by geometric and electronic structure,especially under high current densities.Herein,a newly designed lamella-heterostructured nanoporous CoFe/CoFe_(2)O_(4) and CeO_(2−x),in situ grown on nickel foam(NF),holds great promise as a high-efficient bifunctional electrocatalyst(named R-CoFe/Ce/NF)for water splitting.Experimental characterization verifies surface reconstruction from CoFe alloy/oxide to highly active CoFeOOH during in situ electrochemical polarization.By virtues of three-dimensional nanoporous architecture and abundant electroactive CoFeOOH/CeO_(2−x) heterostructure interfaces,the R-CoFe/Ce/NF electrode achieves low overpotentials for oxygen evolution(η_(10)=227 mV;η_(500)=450 mV)and hydrogen evolution(η_(10)=35 mV;η_(408)=560 mV)reactions with high normalized electrochemical active surface areas,respectively.Additionally,the alkaline full water splitting electrolyzer of R-CoFe/Ce/NF||R-CoFe/Ce/NF achieves a current density of 50 mA·cm^(−2) only at 1.75 V;the decline of activity is satisfactory after 100-h durability test at 300 mA·cm^(−2).Density functional theory also demonstrates that the electron can transfer from CeO_(2−x) by virtue of O atom to CoFeOOH at CoFeOOH/CeO_(2−x) heterointerfaces and enhancing the adsorption of reactant,thus optimizing electronic structure and Gibbs free energies for the improvement of the activity for water splitting.展开更多
基金funded by the National Natural Science Foundation of China(NSFCGrant Nos.42204177,42274219,41974205,42130204,42241155,and 42241133)+5 种基金the Guangdong Basic and Applied Basic Research Foundation-Natural Science Foundation of Guangdong(Grant Nos.2022A1515010257,2022A1515011698,and 2023A1515030132)the Shenzhen Science and Technology Research Program(Grant Nos.JCYJ20210324121403009 and JCYJ20210324121412034)the Macao foundation,the Fundamental Research Funds for the Central Universities(Grant No.HIT.OCEF.2022041)the Shenzhen Key Laboratory Launching Project(Grant No.ZDSYS20210702140800001)the pre-research project on Civil Aerospace Technologies(Grant No.D020103)funded by the China National Space Administration.YuanQiang Chen was also funded by China Postdoctoral Science Foundation(Grant No.2022M720944)supported by the Chinese Academy of Sciences Center for Excellence in Comparative Planetology.
文摘Geomagnetic storms can result in large magnetic field disturbances and intense currents in the magnetosphere and even on the ground.As an important medium of momentum and energy transport among the solar wind,magnetosphere,and ionosphere,field-aligned currents(FACs)can also be strengthened in storm times.This study shows the responses of FACs in the plasma sheet boundary layer(PSBL)observed by the Magnetospheric Multiscale(MMS)spacecraft in different phases of a large storm that lasted from May 27,2017,to May 29,2017.Most of the FACs were carried by electrons,and several FACs in the storm time also contained sufficient ion FACs.The FAC magnitudes were larger in the storm than in the quiet period,and those in the main phase were the strongest.In this case,the direction of the FACs in the main phase showed no preference for tailward or earthward,whereas the direction of the FACs in the recovery phase was mostly tailward.The results suggest that the FACs in the PSBL are closely related to the storm and could be driven by activities in the tail region,where the energy transported from the solar wind to the magnetosphere is stored and released as the storm is evolving.Thus,the FACs are an important medium of energy transport between the tail and the ionosphere,and the PSBL is a significant magnetosphere–ionosphere coupling region in the nightside.
文摘In this investigation effort, we eventually infer that the overall quadrapole pattern of B<sub>y</sub> deflections, in the vicinity of a source in the Earth’s magnetotail, is most likely due to field aligned currents (FACs) and not to Hall currents associated with an X-type collisionless reconnection. This categorically expressed statement is based upon sufficient observational evidence tightly associated with our own suggested model and the preceded works of the same author. Using representative events measured by satellite, our main aim is to describe the nature of the fundamental mechanism determining the polarity of the B<sub>y</sub> deflections associated with intense earthward ionplasma flows. A major finding is that we either observe magnetic flux rope (MFR) like structures (that is, entities having all the morphological features of ropes; i.e., a dipolar signature of B<sub>z</sub> occurring simultaneously with peaked B<sub>y</sub> and B<sub>total</sub> deflections) or mere B<sub>y</sub> deflections, however, the sign for all these (B<sub>y</sub>deflections) is always determined by the satellite placement in north (positive) or south (negative) plasma sheet. Therefore, the MFR-like structures located earthward of the source are most likely pseudo-MFRs;there is neither a tubular topology nor an axial magnetic field, the B<sub>y</sub> deflections are produced by FACs. According to the presented model, a fundamental concept is that both ions and electrons are simultaneously accelerated at the source site;in turn, the earthward streaming electrons (ions) form a bifurcated electron (ion) FAC just outside the electron diffusion region-EDR (IDR). In this way, inside the IDR (and earthward of the source) positive (negative) B<sub>y</sub> deflections in north (south) plasma sheet (PS) are produced due to FACs, and not to (inward) Hall currents as in the context of an X-line. Moreover, the ions form an “ion jet” within the IDR, while just outside this region they produce positive (negative) B<sub>y</sub> deflections in north (south) PS caused by ion FACs. The ion jet in the IDR is enveloped by the bifurcated electron FAC. Eventually, although the resulting pattern of B<sub>y</sub> deflections, due to both electron and ion FACs, is apparently the same with that resulting from Hall currents (in the X-line model), the underlying natural processes are, however, radically different. Certainly, the dominant “spatial entity” within the IDR is the ion jet-current (and not the Hall-electron current). Additional implications of the ion jets are also discussed.
文摘A combined action of plasma convection and pitch-angle diffusion of electrons and protons leads to the formation of plasma pressure distribution in the magnetosphere on the night side, and, as it is known, steady electric bulk currents are connected to distribution of gas pressure. The divergence of these bulk currents brings about a spatial distribution of field-aligned currents, i.e. magnetospheric sources of ionospheric current. The projection (mapping) of the plasma pressure relief onto the ionosphere corresponds to the form and position of the auroral oval. This projection, like the real oval, executes a motion with a change of the convection electric field, and expands with an enhancement of the field. Knowing the distribution (3D) of the plasma pressure we can determine the places of MHD-compressor and MHD-generators location in the magnetosphere. Unfortunately, direct observations of plasma distribution in the magnetosphere are faced with large difficulties, because pressure must be known everywhere in the plasma sheet at high resolution, which in situ satellites have been unable to provide. Modeling of distribution of plasma pressure (on ~ 3-12 Re) is very important, because the data from multisatellite magnetospheric missions for these purposes would be a very expensive project.
基金Supported by the National Natural Science Foundation of China (Grant Nos. CNSF-40474058 and CNSF-40536030)
文摘A 3-dimensional resistive MHD simulation was carried out to study the effect of the upward ions on the field-aligned currents (FACs) in the near-earth magnetotail. The simulation results show that the up-flow ions originating from the nightside auroral oval would drift into the center plasma sheet along the magnetic field lines in the plasma sheet boundary, and have an important effect on the field-aligned currents. The main conclusions include that: 1) the upward-ions mainly affect the field- aligned currents in the near-earth magnetotail (inside 15 Re); 2) the generated FACs in the near-earth region have two types, i.e., Region 1 FAC in the high-latitude and Region 2 FAC in the low-latitude; 3) FACs increase with the enhancement of the upward ion flux; 4) with the same flux of the upward ions, FACs enhance with the increase of the velocity of the up-flow ions; 5) the intensification of FACs is also closely related with the latitude of the upward ions, and the ions from the closed field line region generate larger FACs; 6) the generation of FACs is closely related with By created by the upward ions.
基金Supported by the National Natural Science Foundation of China (Grant Nos. 40474058 and 40536030)the Key Project of the National Natural Science Foundation of China (Grant No. 40390152)+2 种基金Chinese Fundamental Research Project (Grant No. G200000784)Chinese Key Research Project (Grant No. 2006CB805305)the Key Displine Project of Beijing
文摘A three-dimensional (3-D) Hall MHD simulation is carried out to study the roles of initial current carrier in the topology of magnetic field, the generation and distribu- tion of field aligned currents (FACs), and the appearance of Alfvén waves. Consid- ering the contribution of ions to the initial current, the topology of the obtained magnetic field turns to be more complex. In some cases, it is found that not only the traditional By quadrupole structure but also a reversal By quadrupole structure appears in the simulation box. This can explain the observational features near the diffusion region, which are inconsistent with the Hall MHD theory with the total ini- tial current carried by electrons. Several other interesting features are also emerged. First, motions of electrons and ions are decoupled from each other in the small plasma region (Hall effect region) with a scale less than or comparable with the ion inertial length or ion skin depth di=c/ωp. In the non-Hall effect region, the global magnetic structure is shifted in +y direction under the influence of ions with initial y directional motion. However, in the Hall effect region, magnetic field lines are bent in ?y direction, mainly controlled by the motion of electrons, then By is generated. Second, FACs emerge as a result of the appearance of By. Compared with the prior Hall MHD simulation results, the generated FACs shift in +y direction, and hence the dawn-dusk symmetry is broken. Third, the Walén relation in our simulations is consistent with the Walén relation in Hall plasma, thus the presence of Alfvén wave is confirmed.
基金a grant from the National Natural Science Foundation of Chinathe Chinese Academy of Sciences
文摘Field-aligned currents in the inner magnetosphere arc studied by using ISEE-2 magnetometer da-la, A method is proposed to calculate ×B with single-satellite data. From the morphology of ×B in time (or L). a lot of large fluctuations are found in ×B near L = 5.5RE corresponding to the field-aligned currents. Statistical study shows that the field-aligned current in the inner magnetosphere is a function of B, L, MLT and AL. The region of the projections of ×B along the magnetic field line onto the ionosphere is not symmetrical for the geomagnetic pole. The inner boundary is independent of the geomagnetic disturbance, but during substorms the outer boundary shifts equatorward. The spatial distribution of the in- and out-flowing currents is complicated. The region-1-and-2 system is hardly distinguishable.
基金supported by the National Basic Research Program of China(2006CB806305)the National Natural Science Foundation of China(40874088 and 40890163)+1 种基金the Special Fund for Public Welfare Industry(GYHY200806072)State-level Public Welfar Scientific Research Ccourtyard Basic Scentific Research Operation Cost(058904)
文摘Using the east-west geomagnetic disturbance fields observed from stations at mid-latitudes,we investigate the characteristics of field-aligned currents on the nightside during the April 6,2000 superstorm.The results indicate that there is an eastward disturbance on the nightside of Northern Hemisphere during the main phase of magnetic storm,while the interplanetary magnetic field(IMF)is continued southward.The positive disturbances in the postmidnight are larger than that in the premidnight.This suggests that upward field-aligned currents develop on the nightside,when the IMF is directed southward.The peak of upward fieldaligned currents is located in postmidnight,and it will be more obvious at substorm expansion.We get the conclusion that both partial ring current and region-2 field-aligned current shift to dusk sector.The upward region-2 current is decreased at substorm onset,and intensified after it.We also investigate the relationship between the upward field-aligned currents on the nightside and the auroral electrojets at high latitudes.It shows a good correspondence between region-2 current and the westward electrojet in the postmidnight.We suppose that they are both associated with the convection electric field.
基金National Key Research and Development Program of China(2021YFB3700801)。
文摘Low-density short-duration pulsed current-assisted aging treatment was applied to the Ti-6Al-4V-0.5Mo-0.5Zr alloy subjected to different solution treatments.The results show that numerous α_(p) phases redissolve into the new β phase during the pulsed current-assisted aging process,and then the newly formed β phase is mainly transformed into the β_(t) phase,with occasional transition to new α_(p) phase,leading to a remarkable grain refinement,especially for the lamellarαs phases.In comparison to conventional aging treatment,the pulsed current-assisted aging approach achieves a significant enhancement in strength without degrading ductility,yielding an excellent mechanical property combination:a yield strength of 932 MPa,a tensile strength of 1042 MPa,and an elongation of 12.2%.It is primarily ascribed to the increased fraction of β_(t) phases,the obvious grain refinement effect,and the slip block effect induced by the multiple-variantαs colonies distributed within β_(t) phases.
基金supported by the National Natural Science Foundation of China(Nos.92461304 and 52202192)China Postdoctoral Science Foundation(Nos.2020M682338 and 2023T160593)+2 种基金China National Postdoctoral Program for Innovative Talents(No.BX20230329)Zhengzhou Universitythe support from the Center of New Materials and Device of Huazhong University of Science and Technology.
文摘Two-dimensional(2D)MoS_(2) is considered an excellent candidate material for nextgeneration photodetectors.However,the high dark current and low photocurrent in MoS_(2) devices severely hinder their practical application.Strategies for suppressing dark current and enhancing photocurrent should be explored.Herein,we propose a modification strategy for MoS_(2) by utilizing Ag_(70) nanoclusters(NCs)as electron reservoirs and photoabsorbers to suppress dark current and enhance the photocurrent of 2D MoS_(2) photodetector.Remarkably,the dark current is effectively suppressed by four orders of magnitude,while the photocurrent is enhanced by over tenfold upon modification with Ag_(70) NCs,compared to the pristine MoS_(2) photodetector.The reduction in dark current is attributed to charge transfer from MoS_(2) to Ag_(70) NCs owing to the strong electronwithdrawing property of Ag_(70) NCs.The increase in photocurrent benefits from enhanced optical absorption of the photodetector after Ag_(70) NCs modification and the subsequent injection of photoexcited electrons from Ag_(70) NCs to MoS_(2).Compared to isolated MoS_(2),the modulated photodetector shows exceptional improvements in several key figures of merit(such as responsivity,detectivity,external quantum efficiency,and photoswitching on/off ratio).This study opens up new avenues for building high-performance 2D MoS_(2) photodetectors.
基金DAAD Sandwich Scholarship and the National Natural Science Foun-dation of China (Grant No. 40390150)
文摘With geomagnetic measurements on board of CHAMP satellite, the characteristics of global large-scale field-aligned currents (FACs) in the topside ionosphere are investigated along with their responses to interplanetary conditions for the superstorm of November, 2003. It is found that (1) The storm-time FAC densities enhanced greatly in comparison with quiet period and the enhancements show hemispheric asymmetry of both summer-winter and sunlit-dark. (2) For the first time, it is revealed that the lati-tude-integrated FAC density is controlled mainly by solar wind dynamic pressure rather than IMF. (3) FACs expanded equatorward dramatically, with the lowest latitude being 45° MLat or more; on the day-side this expansion was controlled directly by IMF Bz, showing an interaction time scale of about 25 min in the solar wind-magnetosphere-ionosphere coupling system, and a nonlinear saturation of the equatorward expansion when IMF Bz < -30 nT; while on the nightside, the expansion and recovery lagged about 3 h behind the IMF changes but nearly in phase with changes of SYM-H index. (4) During the storm main phase, the nightside FAC latitude coverage extended to 25° or wider, appearing multi-sheet current structure with more than 10 sheets.
基金supported by the National Natural Science Foundation of China (42250101)the Macao Foundation. The computation made use of the high-performance computing resources at the center of the MSS data processing and analysis。
文摘Accurate modeling of Earth's ionospheric F-region currents is essential for refining geomagnetic field models and understanding magnetosphere-ionosphere coupling.In this study,we develop averaged models to characterize F-region currents using magnetic data from the MSS-1(Macao Science Satellite-1) and Swarm satellite missions.Our approach employs a toroidal field representation,utilizing spherical harmonics to capture spatial variations and Fourier series to represent temporal dynamics.Two models,Model-A and Model-B,derived from distinct datasets,are constructed to represent current patterns at altitudes of 450 km and 512 km,respectively.Our models successfully capture the primary spatial structures and seasonal variations of polar field-aligned currents.Additionally,they accurately reproduce the localized inter-hemispheric field-aligned currents observed in mid and low latitudes during solstices,particularly between 14:00 and 16:00 magnetic local times.These findings enhance our understanding of ionospheric F-region currents and contribute to more precise geomagnetic field modeling.
基金supported by National Natural Science Foundation of China under Grant Nos.11505240,11375196 and 11405174the National ITER program of China under Contract No.2014GB113000
文摘Field-aligned coordinates have been implemented in the gyrokinetic semi-Lagrangian code NLT, Ye et al （2016 J. Comput. Phys. 316 180）, to improve the computational efficiency for the numerical simulations of tokamak turbulence and transport. 4D B-spline interpolation in field- aligned coordinates is applied to solve the gyrokinetic Vlasov equation. A fast iterative algorithm is proposed for efficiently solving the quasi-neutrality equation. A pseudo transform method is used for the numerical integration of the gyro-average operator for perturbations with a high toroidal mode number. The new method is shown to result in an improved code performance for reaching a given accuracy. Some numerical tests are presented to illustrate the new methods.
基金supported in part by Natural Science Foundation of Jiangsu Province under Grant BK20230255Natural Science Foundation of Shandong Province under Grant ZR2023QE281.
文摘The multi-terminal direct current(DC)grid has extinctive superiorities over the traditional alternating current system in integrating large-scale renewable energy.Both the DC circuit breaker(DCCB)and the current flow controller(CFC)are demanded to ensure the multiterminal DC grid to operates reliably and flexibly.However,since the CFC and the DCCB are all based on fully controlled semiconductor switches(e.g.,insulated gate bipolar transistor,integrated gate commutated thyristor,etc.),their separation configuration in the multiterminal DC grid will lead to unaffordable implementation costs and conduction power losses.To solve these problems,integrated equipment with both current flow control and fault isolation abilities is proposed,which shares the expensive and duplicated components of CFCs and DCCBs among adjacent lines.In addition,the complicated coordination control of CFCs and DCCBs can be avoided by adopting the integrated equipment in themultiterminal DC grid.In order to examine the current flow control and fault isolation abilities of the integrated equipment,the simulation model of a specific meshed four-terminal DC grid is constructed in the PSCAD/EMTDC software.Finally,the comparison between the integrated equipment and the separate solution is presented a specific result or conclusion needs to be added to the abstract.
基金Core Research Institute Basic Science Research Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Education(No.2018R1A6A1A03025242)in part by the research grant of Kwangwoon University in 2024。
文摘Advanced OER/HER electrocatalytic alternatives are crucial for the wide adaptation of green hydrogen energy.Herein,Ru/NiMnB spherical cluster pillar(SCP),denoted as Ru/NiMnB,is synthesized using a combination of electro-deposition and hydrothermal reaction.Systematic investigation of Ru doping in the NiMnB matrix revealed significant improvements in electrocatalytic performance.The Ru/NiMnB SCPs demonstrate superior OER/HER activity with low overpotentials of 150 and 103 mV at 50mA/cm^(2)in 1 M KOH,making them highly competitive with state-of-the-art electrocatalysts.Remarkably,the Ru/NiMnB SCPs exhibit a low 2-E cell voltage of 2.80 V at ultra-high current density of 2,000 m A/cm^(2)in 1 M KOH,outperforming the standard benchmark electrodes of RuO_(2)||Pt/C,thereby positioning Ru/NiMnB as one of the best bifunctional electrocatalysts.These SCPs exhibit exceptional high-current characteristics,stability and corrosion resistance,as evidenced by continuous operation at 1,000 mA/cm^(2)high-current density for over 150 h in 6 M KOH at elevated temperatures under harsh industrial conditions.Only a small amount of Ru incorporation significantly enhances the electrocatalytic performances of NiMnB,attributed to increased active sites and improved intrinsic properties such as conductivity,adsorption/desorption capability and reaction rates.Consequently,Ru/NiMnB SCPs present a promising bi-functional electrode concept for efficient green H_(2)production.
基金funding from the European Union’s Horizon 2020 research and innovation program through the European IMPULSE project under Grant Agreement No.871161from LASERLAB-EUROPE V under Grant Agreement No.871124+6 种基金from the Grant Agency of the Czech Republic(Grant No.GM23-05027M)Grant No.PDC2021120933-I00 funded by MCIN/AEI/10.13039/501100011033by the European Union Next Generation EU/PRTRsupported by funding from the Ministerio de Ciencia,Innovación y Universidades in Spain through ICTS Equipment Grant No.EQC2018-005230-Pfrom Grant No.PID2021-125389O A-I00 funded by MCIN/AEI/10.13039/501100011033/FEDER,UEby“ERDF A Way of Making Europe”by the European Unionfrom grants of the Junta de Castilla y León with Grant Nos.CLP263P20 and CLP087U16。
文摘This work demonstrates experimentally the close relation between return currents from relativistic laser-driven target polarization and the quality of the relativistic laser–plasma interaction for laser-driven secondary sources,taking as an example ion acceleration by target normal sheath acceleration.The Pearson linear correlation of maximum return current amplitude and proton spectrum cutoff energy is found to be in the range from~0.70 to 0.94.kA-scale return currents rise in all interaction schemes where targets of any kind are charged by escaping laser-accelerated relativistic electrons.Their precise measurement is demonstrated using an inductive scheme that allows operation at high repetition rates.Thus,return currents can be used as a metrological online tool for the optimization of many laser-driven secondary sources and for diagnosing their stability.In particular,in two parametric studies of laser-driven ion acceleration,we carry out a noninvasive online measurement of return currents in a tape target system irradiated by the 1 PW VEGA-3 laser at Centro de Láseres Pulsados:first the size of the irradiated area is varied at best compression of the laser pulse;second,the pulse duration is varied by means of induced group delay dispersion at best focus.This work paves the way to the development of feedback systems that operate at the high repetition rates of PW-class lasers.
基金Supported by National Natural Science Foundation of China,No.82205298Natural Science Foundation of Hunan Province,No.2023JJ30462+1 种基金Hunan Provincial Department of Science and Technology,No.2023SK2045,No.22JBZ007,No.Z2023XJYQ07,No.B2024007,and No.Z2023JB012024 Graduate Innovation Topics,No.2024CX031.
文摘BACKGROUND Diabetic gastroparesis(DGP)disrupts gastric motility.Electroacupuncture(EA)at Zusanli(ST36)may alleviate DGP symptoms via neural pathways.AIM To investigate how EA current intensities at ST36 regulate neural pathways and improve gastric motility in DGP models.METHODS A DGP model was established using intraperitoneal injection of streptozotocin.Gastrointestinal motility was measured in rats after 2 weeks of continuous EA at ST36.Current intensity was selected as 0.5 mA,1 mA,and 3 mA.Gastric electrodynamics were detected by recording and analyzing the number of gastric discharges.The gastric emptying rate and propulsion rate of the small intestine were measured to assess dynamic gastrointestinal function.Hematoxylin-eosin staining was conducted to measure histopathological changes in the gastric sinus.Reverse transcription-polymerase chain reaction was conducted to determine mRNA levels of Rho guanine nucleotide-binding protein A and Rho-associated coiled-coil forming protein kinase.Western blotting was conducted to determine the expression levels of choline acetyltransferase,tyrosine hydroxylase,Rho guanine nucleotide-binding protein A,and Rho-associated coiled-coil forming protein kinase.Immunofluorescence staining in the stomach was conducted to detect the distribution of C-kit,an interstitial cell of Cajal marker.An enzymelinked immunosorbent assay was conducted to detect serum levels of acetylcholine and norepinephrine.RESULTS Treatment with EA improved gastric emptying and gastric smooth muscle disorders in rats with DGP,mitigated pathological damage,and restored the function of interstitial cells of Cajal.In addition,different current intensities of EA affected gastrointestinal function of rats with DGP.The 0.5 mA,1 mA,and 3 mA EA groups all improved gastrointestinal function.0.5 mA EA increased acetylcholine levels by increasing protein expression of choline acetyltransferase(P<0.05),thereby upregulating vagus nerve activity and enhancing parasympathetic nerve regulation.3 mA EA increased norepinephrine levels(P<0.05)by increasing protein expression of tyrosine hydroxylase,thereby activating the sympathetic nervous pathway.1 mA coordinated the function of the vagus and sympathetic nerves to improve gastrointestinal motility.CONCLUSION EA with ST36 improved gastric motility in rats with DGP.0.5 mA EA activated the vagus nerve,while 3 mA EA regulated gastrointestinal motility by activating the sympathetic nerves.
基金supported by the Fundamental Research Funds for the Central Universities(No.FRF-BD-23-01).
文摘Non-metallic inclusions in steel are a significant challenge,affecting material properties and leading to issues such as stress concentration,cracking,and accelerated corrosion.Current methods for removing inclusions,including bubble,electromagnetic stirring,filtration separation,fluid flow,and sedimentation,often struggle with the removal of fine inclusions.Apart from these known methods,pulsed electric current(PEC),as an emerging technology,has demonstrated immense potential and environmental advantages.PEC offers adjustable current parameters and simple equipment,making it an attractive alternative to traditional methods.Its green energy-saving features and excellent results in regulating inclusion morphology and migration,as well as inhibiting submerged entry nozzle(SEN)clogging,make it a promising technology.In comparison to continuous current technology,PEC has shown significant advantages in regulating inclusions,not only improving purification efficiency but also demonstrating outstanding performance in flow stability and energy consumption.The ability of PEC to efficiently reduce inclusion numbers enhances the purity and quality of molten steel,improving its mechanical properties.Currently,the theoretical basis for controlling the movement of inclusions by current is mainly composed of three major theories:the double electric layer theory,electromagnetic force reverse separation theory,and electric free energy drive theory.These theories together form an important framework for researchers to understand and optimize the behavior of impurity movement controlled by electric current.Looking ahead,PEC is expected to pave the way for new solutions in directional regulation of inclusion migration,efficient inclusion removal,SEN clogging prevention,and the purification of molten steel.
基金supported by the the National Key R&D Program of China(2022YFB3803500)the Natural Science Foundation of Hubei Province(2021CFA066).
文摘Micron-sized silicon(μSi)is a promising anode material for next-generation lithium-ion batteries due to its high specific capacity,low cost,and abundant reserves.However,the volume expansion that occurs during cycling leads to the accumulation of undesirable stresses,resulting in pulverization of silicon microparticles and shortened lifespan of the batteries.Herein,a composite film of Cu-PET-Cu is proposed as the current collector(CC)forμSi anodes to replace the conventional Cu CC.Cu-PET-Cu CC is prepared by depositing Cu on both sides of a polyethylene terephthalate(PET)film.The PET layer promises good ductility of the film,permitting the Cu-PET-Cu CC to accommodate the volumetric changes of silicon microparticles and facilitates the stress release through ductile deformation.As a result,theμSi electrode with Cu-PET-Cu CC retains a high specific capacity of 2181 mA h g^(-1),whereas theμSi electrode with Cu CC(μSi/Cu)exhibits a specific capacity of 1285 mA h g^(-1)after 80 cycles.The stress relieving effect of CuPET-Cu was demonstrated by in-situ fiber optic stress monitoring and multi-physics simulations.This work proposes an effective stress relief strategy at the electrode level for the practical implementation ofμSi anodes.
基金sponsored by the National Natural Science Foundation of China(Nos.5210125 and 52375422)the Science Research Project of Hebei Education Department(No.BJK2023058)the Natural Science Foundation of Hebei Province(Nos.E2020208069,B2020208083 and E202320801).
文摘The stability and electrocatalytic efficiency of transition metal oxides for water splitting is determined by geometric and electronic structure,especially under high current densities.Herein,a newly designed lamella-heterostructured nanoporous CoFe/CoFe_(2)O_(4) and CeO_(2−x),in situ grown on nickel foam(NF),holds great promise as a high-efficient bifunctional electrocatalyst(named R-CoFe/Ce/NF)for water splitting.Experimental characterization verifies surface reconstruction from CoFe alloy/oxide to highly active CoFeOOH during in situ electrochemical polarization.By virtues of three-dimensional nanoporous architecture and abundant electroactive CoFeOOH/CeO_(2−x) heterostructure interfaces,the R-CoFe/Ce/NF electrode achieves low overpotentials for oxygen evolution(η_(10)=227 mV;η_(500)=450 mV)and hydrogen evolution(η_(10)=35 mV;η_(408)=560 mV)reactions with high normalized electrochemical active surface areas,respectively.Additionally,the alkaline full water splitting electrolyzer of R-CoFe/Ce/NF||R-CoFe/Ce/NF achieves a current density of 50 mA·cm^(−2) only at 1.75 V;the decline of activity is satisfactory after 100-h durability test at 300 mA·cm^(−2).Density functional theory also demonstrates that the electron can transfer from CeO_(2−x) by virtue of O atom to CoFeOOH at CoFeOOH/CeO_(2−x) heterointerfaces and enhancing the adsorption of reactant,thus optimizing electronic structure and Gibbs free energies for the improvement of the activity for water splitting.
